Process for the separation of impurities from nickel chloride solutions

ABSTRACT

A process for the separation of metallic impurities, from aqueous nickel chloride solutions by selective liquid/liquid extraction between said aqueous phase containing the said metallic impurities in chloride form and an organic phase containing a trialkyl sulfonium chloride in the form of a solution in an organic diluent substantially immiscible with water, such that at least one of the said metallic valuables is selectively transferred from the aqueous phase to the organic phase, characterized by the fact that the said aqueous phase is substantially neutral and that it presents a total concentration in chloride ions equal at least to 7 gram equivalents/liter.

O United States Patent [151 3,660,020 Gandon et al. 1 May 2, 1972 54PROCESS FOR THE SEPARATION ()1? 3,251,646 5/1966 Alon et al ..23/50 R UT S FROM NICKEL 3,380,80l 4/1968 Williams et al ..23/5O R 3,055,7549/l962 Fletcher ..23/5O R UX [72] Inventors: Louis Gandon; ChristianBozec; Philippe Primary ExaminerHerbert T. Carter Lenoble, all Of Le HFrance Att0rney-Oberlin, Maky, Donnelly & Renner [73] Assignee: LeNickel, Paris, France [57] ABSTRACT [22l Filed: Aug. 7, 1970 A processfor the separation of metallic impurities, from aque- 1 PP No.1 62.190ous nickel chloride solutions by selective liquid/liquid extractionbetween said aqueous phase containing the said metallic 39 Foreign A fiti priority Data impurities in chloride form and an organic phasecontaining a 2 196 trialkyl sulfonium chloride in the form of a solutionin an or- 1 9 France "6922701 ganic diluent substantially immisciblewith water, such that at least one of the said metallic valuables isselectively transa [5-] CL "23/87 23/50 0 ferred from the queous Phaseto the organic Phase, charac. 51 1m. 01 C0lg 53/08 terized by the factthat Said aqueous Phase is subsamiauy [58] Field of Search g l 19 101neutral and that it presents a total concentration in chloride l ionsequal at least to 7 gram equivalents/liter. [56] References cued 8Claims, No Drawings UNITED STATES PATENTS 3.507.645 4/1970 Spitzer etal. ..23/50 R PROCESS FOR THE SEPARATION OF IMPURITIES FROM NICKELCHLORIDE SOLUTIONS The invention is concerned with the separation ofmetallic impurities contained in aqueous nickel chloride solutions.

The term metallic impurities" embraces all of the metallic elements, andin particular metal salts and the ions, complex or not, from which theyare derived, which are generally usually contained in industrial nickelchloride solutions.

The present invention is concerned in particular with the separation ofcobalt and iron from industrial nickel chloride solutions resulting fromindustrial processes for the production of nickel.

The elimination ofiron and cobalt generally contained in industriallyobtained nickel chloride solutions is already known. The oldesttechnique consists in precipitating the iron and cobalt in the form oftheir trivalent oxides after oxidation of the chloride solutions undercontrolled conditions of pH. Other more recent methods make use of solidanion exchangers such as anion exchange resins, or liquid ion exchangerssuch as long chain tertiary amines or quaternary amines; in the case ofliquid exchangers, the process employs a liquid/liquid extraction, theactive agent being itself diluted in a solvent having little or nomiscibility with water, adapted to absorb the complex and maintain it instable form. There has also been proposed exchangers of mineral ions,such as titanium phosphates but the latter have the inconvenience ofhydrolysing too easily.

All the aforesaid processes have defects which make their industrialapplication either laborious or subject to risks. Indeed in the oldesttechnique employing the precipitation of iron and cobalt by oxidation bymeans of chlorine, ozone, or hypochlorites considerable difficulties aremet, notably the filtration of the hydroxides which are generallyprecipitated in colloidal form and the entrainment of substantialquantities of nickel which are adsorbed by these precipitates.

In the case of material acting as an ion exchanger, when it is concernedwith anion resins of the quaternary ammoniumpolystyrene type, as forexample AMBERLITE IRA 400, or liquid amines such as ALAMINE 336" orALIQUAT 336 5," one proceeds, for the formation of complex chlorideamions of cobalt and iron, with the massive addition of a chlorinatingagent, generally free hydrochloric acid, which leads to considerabletechnical difficulties in putting the process into practice. Moreover,the separated solution of nickel chloride is loaded with hydrochloricacid which is practically impossible to eliminate. In addition to thetechnical difficulties which would be encountered in transporting suchacid solutions, it is impossible to use them as such for the recovery ofnickel by known methods like electrolysis with insoluble anodes orreduction by hydrogenation under pressure. However, it is clear that,without these drawbacks, the separation by liquid/liquid extractionwould present marked advantages due to the facility of carrying out theprocess and the possibility of conducting the purification operations ina continuous and controllable manner. Indeed, metallic elements capableof forming chloride complexes, for example cobalt, can be extractedselectively from an aqueous phase to an organic phase containing acomplexing agent and then recovered separately by washing this organicphase with water. After this extraction, the aqueous phase contains thenickel in chloride form, and in its nickel concentration does not changenotably during the extraction operation.

The applicants have found that it is possible to form complexes in theorganic phase without the presence of hydrochloric acid in the aqueousphase by using sufficiently concentrated neutral chloride saltsolutions. Indeed, the applicants have established that, when theconcentration of chlorine ions in the aqueous phase reaches a sufficientvalue, above 7 gram equivalents/liter, it is no longer necessary toprovide, in the form of hydrochloride acid, complementary chlorine ionsto facilitate the passage of the chlorocobaltic or chloroferriccomplexes to the organic phase.

It is besides, known to use sulfonium salts as complexing agents for theseparation of metallic valuables in an aqueous solution. With this knowntechnique, the aqueous phase to be purified must be strongly acid. Forexample, for the separation of nickel from cobalt in an aqueous solutionof their chlorides, the aqueous phase must contain 200 to 400 grams offree HCl per liter of solution; due to this fact the solution to betreated cannot be very concentrated in salts of nickel and cobalt.

Further, according to the known technique, it is necessary in order tooptimize the effect of the complexing agent, to dilute the sulfoniumsalt in a polar organic solvent, for example a chloride of an aliphatichydrocarbon having at least one mobile hydrogen atom. This type ofsolvent is not always suitable for the organic phase of extraction,notably in the case where it is desired to treat an aqueous phase ofhigh density.

The applicants have found that the organic solvent can advantageously bea relatively light solvent, containing no chlorine atoms and showinglittle or no solubility in water. for example an ester, an ether oxideor a ketone of low molecular weight. Moreover, the combined effect ofthis type of solvent and a suitable concentration of complexing agent toform the organic extracting phase results in a considerable diminishingin losses of complexing agent in the course of the extraction operation.

It is thus established that it is possible to use sulfonium salts forthe separation of cobalt from nickel, and cobalt contained inconcentrated aqueous chloride solution, practically in the absence offree acid, and by using a solvent capable of ensuring a good separationbetween the aqueous and organic phases and a convenient rate ofextraction with a minimum loss of complexing agent.

The complexing agent is an alkyl sulfonium chloride with the generalformula in which R is a CH radical, and R and R are alkyl radicalshaving seven to l3 atoms of carbon. Preferably the complexing agent is adi-sec (C to C alkyl) methyl-sulfonium chloride and more particularlydi-sec-decyl-methyl sulfonium chloride.

The complexing agent is dissolved in an organic solvent slightly or notat all miscible with water, preferably an alcohol ester with a molecularweight less than butyl, amyl and hexyl acetates and propionates, i.e.,less than 10 carbon atoms, or a ketone such as methyl-isopropyl ketone,methyl-isobutyl ketone and di-isobutyl ketone, or an ether oxide such asbutyl oxide, or a mixture of other organic solvents with one of theaforesaid solvents. Halogen-containing solvents such as l, 2-dichloroethane, chloroform, trichloroethylene, bromoform,dichlorobenzene, are however, equally suitable.

Aqueous solutions to be treated will generally be provided from one ofthe stages of nickel production process. These are, for example,concentrated chloride solutions obtained by dissolving, withhydrochloric acid, by-products resulting from the preferentialelimination of cobalt from nickel solutions, either by oxidation, or bysulfuration, or solutions resulting from the dissolving in waterofchlorides having served to wash a nickel matte during the treatmentcalled Chloridizing Fusion. Such solutions can also result from theattack by chlorine or hydrochloric acid on any nickeliferous materialsuch as used catalysts ores and alloys containing both nickel andcobalt.

In the process according to the invention, the aqueous phase constitutedby the chloride salt solution is contacted with mechanical agitation,with an organic phase containing the complexing agent and the solvent,which is preferably butyl acetate, for less than 5 minutes and in avolumetric ratio organic phase aqueous phase between one-half and ten,and preferably between one and three. The mixture is then allowed torest and, after decemtation, the two phases are separated. The organicphase containing cobalt chloride is washed by a second aqueous phase,containing water possibly acidified, in a volumetric ratio organic phasesecond aqueous phase between one and forty, this operation giving aregenerated organic phase and a cobalt-iron aqueous phase moreconcentrated in cobalt chloride as the volumetric ratio organic phasewater is greater during washing. The organic phase thus regenerated canbe used again for a new extraction. The cobalt-iron aqueous phase canequally well be used again for another washing operation of the organicphase to the amount of a concentration of cobalt chloride of the orderof 130 g. of CoCl, per liter. These operations are preferably carriedout at ambient temperature, although both higher or lower temperaturesare equally suitable.

The abovedescribed treatment is the simplest way of carrying out theprocess according to the invention, but it can, of course, and withoutdeparting from the scope of the invention be carried out withmodifications as for example the realization of a counter-currenttreatment in contacting apparatus such as packing columns, rotary disccolumns, pulsating columns, multi-stage centrifugal extractors,compartmented apparatus of the type MIXER SETTLER, or multiplehydrocyclones.

Preferably the process according to the invention is applied to thetreatment of chloride solutions obtained from processes for producingnickel, these solutions containing nickel and cobalt in a weight ratiobetween six and one-half, but the technique can equally well andadvantageously be extended to the purification of solutions of nickelchloride much less concentrated in cobalt, containing, for example, 40parts by weight of nickel to 1 part by weight of cobalt.

The concentration of the complexing agent organic phase can vary between0.2 and l mole/liter, but it is preferably between 0.3 and 0.5moles/liter, taking into account the fact that with low concentrationsthe selectivity with respect to the chlorinated complex is higher butentails a considerable loss of complexing agent, while at higherconcentrations, the selectivity is less but entails smaller losses.

The process according to the present invention will be better understoodby the following examples given solely by way of illustration.

EXAMPLE 1 Influence of the solvent A substantially neutral chloridesolution containing 152 g./l. of Ni and 25.2 g./l. of Co, having aconcentration of chlorine ions of 6 gram equivalents/liter and a weightratio Ni/Co of about 6, has been obtained by dissolving in hydrochloricacid a sludge obtained from the selective oxidation of cobalt by sodiumhypochlorite during the treatment of a sulfate solution with impurenickel resulting from the reaction of sulfuric acid with nickeliferouswastes rich in cobalt.

in the course of a series of comparative experiments, 500 ml of thissolution are each time placed in contact, in a decanting vessel, with aliter of a solution containing 0.3 mole of di-secdecyl-methyl-sulfoniumchloride in one of the following solvents:

l, 2 dichloroethane, trichloroethylene, bromofonn, l, 2 dichlorobenzene,butyl acetate, and a mixture of 75 percent trichloroethylene and 25percent bromoform. After mechanical agitation for 1 minute it is left todecant. The times for decanting and clarification of the phases arenoted and the phases are then separated. The organic phase is washed by500 ml of acidified water and the degree of separation is determined byanalysis of the aqueous phase after this operation. The lossesrof activematerial by entrainment in the aqueous phases are evaluated by theamount of sulfonium compound before and after the extraction operation.The results obtained are set out in Table I hereunder, in which thecapacity of extraction of the sulfonium compound is expressed in gramsof cobalt recovered to l kilogram of raw active material supplied to aconcentration of 2 equivalents per kilogram.

TABLE I Selectivity of passage of metals into the Losses organicCapacity (kg. 01' Duration phase of extracactive 01' decantweight oftion (g. of material ing of cobalt] Co to kg. to kg. phases weight of ofactive of Co Solvent (minutes) nickel) material) extracted)1,2-dichloroethanc 10 1, 000 48 3.0 Trichloethylene T 8 40 2. OBromolorrn 1 3 1, 000 37 l, 5 1,2-dichlorobenzene. 12 12 48 1.0Trichloroethylene plus bromolorm :25 by volume 3 1 000 40 1.5Butylacetat-e. 3 3 38 0. 1

As shown iii Table l the nature of the solvent influences not v EXAMPLE2 Influence of the concentration of the complexing agent in the organicphase 1 volume of a neutral chloride solution containing 137 g./l.

of Ni and 70 g./l. of Co having a weight ratio Ni/Co substantially equalto 2 and a concentration of 7 gram equivalents of chlorine ions/liter iscontacted in a decanting vessel, with 2 volumes of an organic solutionof the same sulfonium compound as in Example 1 dissolved in butylacetate with respective concentrations of 0.3, 0.4 and 0.5 mole/liter.It is agitated for 1 minute and is left to decant. The two phases are Iseparated, recovered and anaiyzed, the results of extraction being givenin Table ll hereunder:

TABLE II Concentration Selectivity of Capacity (g. of of sulfoniumpassage of metal in Co to kg. of

derivative in organic phase active material butyl acetate weight ofcobalt/ weight of nickel 0.3M 40 52 0.4M 12 48 0.5M 7 32 It will beclear that when the concentration of the complexing agent increases inthe organic phase, the selectivity of the sulphonium compositionrelative to the cobalt decreases appreciably. The same goes for thecapacity of absorption expressed in weight of cobalt retained per kg ofactive material employed.

xAivii ui's influence of the concentration of the solution to bepurified Examples l and 2 show that the optimal concentration of thecomplexing agent dissolved in butyl acetate is of the order of 0.3mole/liter. For this concentration of 0.3M of the same 75 sulfoniumderivative there is varied the concentration of the is equal to 3. TableIII hereunder sets out the results of the extraction.

TABLE III Metallic valuables passed into the organic phase weight ofcobalt/ Concentration of aqueous solution treated (in equivalentschlorine Capacity (g. of Co per kg. of active material ions/liter weightof nickel It will be clear that the concentration of salts, expressed inchlorine ions, is a determining factor. Indeed, the selectivityincreases very rapidly with this concentration and, in the conditions ofExample 3, becomes excellent for an amount of Cl above 7equivalents/liter.

EXAMPLE 4 Influence of the weight ratio Ni/Co on the selectivity of theextraction There is used a solution of the same sulfonium derivative inbutyl acetate with a concentration of 0.3 mole/liter with a volumetricratio equal to 2. The weight ratio Ni/Co is varied in salt solutioncomposed of a mixture of C C1 Ni C1 having a constant concentration ofchlorine ions of 7 gram equivalents/liter. Table IV hereunder gives theresults of the extraction:

It will be clear that the selectivity diminishes proportionately to theincrease of the weight ratio Ni/Co in the treated solution. Theinflexion threshold of selectivity with respect to the cobalt is betweenthe weight ratios Ni/Co equal to 2 and to 6.

EXAMPLE 5 organic phase Influence of volumetric ratio aqueous phase Thesolution of Example 3 is taken, the weight ratio being 1.7 and theconcentration in C1 being brought to 7 gram equivalents/liter. Onevaries essentially the volumetric proportion between the organic phaseand the aqueous phase, the concentration in the organic phase beingmaintained at 0.3

mole/liter. The volumetric ratios between the phases have been studiedfor the values between 2 and 8. Table V hereunder sets out the resultsof the extraction:

TABLE V Metallic valuables passed into the organic phase Ratio ofvolumes organic phase/ aqueous phase Capacity (g. of Co per kg. ofactive material) It can be seen that the selectivity with respect to thecobalt diminishes when the volumetric ratio organic phase aqueous phaseincreases.

EXAMPLE 6 Description of operations for a concentrated separation of Coand Ni in a representative chloride solution of an industrial treatmentSludges, resulting from a preferential precipitation of cobalt from asolution of nickel salt in the course of purification, are entirelydissolved in concentrated hydrochloric acid. The obtained neutralsolution contains at a temperature of about 60 C, 178 g./l. of Ni and101 g./l. of Co, at 9.5 equivalents/liter Cl.

Taking into account the information given in the abovedescribedexamples, this solution is treated in several stages of extraction asindicated in Table VI hereunder. Between each stage of extraction theaqueous phase is brought, by evaporation, to its initial concentrationof chlorine ions, this being controlled by a measure of density; theorganic phase is washed by water lightly acidified by HCl which has theeffect, on the one hand, of liberating cobalt in the form of an aqueouschlorine solution, and, on the other hand, of regenerating the activematerial contained in the butyl acetate. The organic phase is used anewfor the following extraction stage.

Table VI hereunder illustrates the performances of the procedureaccording to the invention which in as little as six stages permitsreduction from 0.57 to 0.0095 of the weight ratio Co/Ni in thenickel-iron solution, 98.3 percent cobalt being extracted in the fonn ofan aqueous solution containing 0.57 percent by weight of nickelcalculated relative to the nickel. The seventh stage of extractionfurther reduces the amount in cobalt of the nickel-iron solution sincethe weight ratio Co/N i in the final solution is 0.000625; however thislast TABLE VI Volu- I metric ratio, Amount (parts by weight) organicCobalt Extracphase] Aqueous phase Organic phase extracted, tion aqueouspercent stage phase Nickel Cobalt Nickel Cobalt parts Start 213 121 1st3 213 88. 49 0.00 32. 51 26. 1) 2nd 3 212. 68. 35 0. 25 30. 14 24.2 3rd2 212. 75 39. 38 0.00 18.97 15. 1 4th 2 212.65 23.02 0. 10 16. 36 13. 65th 2 212. 37 8. 39 0. 28 14. 63 12. 1 6th 1 212. 32 2.02 0. 05 6. 37 5.2

Total parts 0. 68 118.98 98. 3

Total 5.14 120.87 99. 9

result has been attained to the detriment of the purity of thecobalt-iron solution corresponding to this seventh stage. This does notrepresent an inconvenience since the organic phase containing cobaltsoiled with nickel can be recycled without inconvenience to the firststage of extraction during the latter the nickel is displaced by thecobalt contained in the initial raw solution to be purified.

By the analysis of di sec (C alkyl)-methyl sulfonium chloride in theregenerated organic phase, it can be seen that the losses by entrainmentin the aqueous solutions or by degradation have been very small, lessthan 0.05 kg for a kg extracted of cobalt.

It will be evident to those skilled in the art that this technique isperfectly suitable for counter-current liquid/liquid extractionprocesses which allow equivalent performances with a limited number ofextraction stages.

What is claimed is:

1. In a process for the separation of metallic impurities from aqueousindustrial nickel chloride solutions, by selective liquid/liquidextraction between said aqueous phase containing the said metallicimpurities in chloride form and an organic phase containing atrialkylsulfonium chloride in the form of a solution in an organicdiluent substantially immiscible with water, such that at least one ofthe said metallic impurities is selectively transferred from the aqueousphase to the organic phase, the improvement which comprises the saidaqueous phase being substantially neutral and having a totalconcentration in chlorine ions equal at least 7 gramequivalents/liter.

2. A process according to claim 1, wherein the improvement furthercomprises an organic diluent comprising a nonpolar and relatively lightsolvent containing no chlorine atoms.

diluent is selected from the group consisting of alcohol esters,ether-oxides and ketones.

4. A process according to claim 3, wherein said organic diluent isselected from the group consisting of butyl acetate, amy acetate,hexylacetate, butyl propionate, amyl propionate, hexyl propionate,methyl-isopropyl ketone, methyl-isobutyl ketone, di-isobutyl ketone, andbutyl oxide.

5. A process according to claim 3, wherein the organic diluent is butylacetate.

6. A process according to claim 1, which is arranged to be continuouslyoperated, the organic phase used for the selective extraction of theaqueous solution being regenerated by being placed in contact with asecond aqueous phase selected from water and water acidified byhydrochloric acid, and used for a new extraction.

7. A process according to claim 6, applied to the separation of cobaltchloride from nickel chloride aqueous solutions and operated in amulti-stage operation providing several distinct organic phases, saidsecond aqueous phase being used for the successive regeneration of saiddistinct organic phases until the concentration of cobalt chloride inthe said second aqueous phase reaches grams per liter.

8. A process according to claim 1, wherein the tri-alkylsulfoniumchloride conforms to the formula wherein R is a Cl-l radical and R and Rare alkyl radicals of from seven to 13 carbon atoms.

i i 1 i i HNQTEED eimes PATENT OFFICE QETgFECATE CURREQTKN en 1,660,026Dated May 2, 1972' Invento'r(s} LOUIS: GANDGH ET ALQ It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown belew:

In the heading of the "patent, item {30] the 7 French a priorityapplication should be correctly identified as application number 6927701rather than 6922701.-

Signed and seek-xi this 19th clay of November 1974.

(SEAL; Attes't:

MCCOY Ma GIBSON JR. Attesting Officer C. MARSHALL DANN I Commissioner ofPatents mm PO-iOSO 10-"9 USCOMM-DC ooa-ns-pos W LL54 GOVERNMENT PRINTINGOFFICE I "I9 0-866-834

2. A process according to claim 1, wherein the improvement furthercomprises an organic diluent comprising a non-polar and relatively lightsolvent containing no chlorine atoms.
 3. A process according to claim 2,wherein said organic diluent is selected from the group consisting ofalcohol esters, ether-oxides and ketones.
 4. A process according toclaim 3, wherein said organic diluent is selected from the groupconsisting of butyl acetate, amy acetate, hexylacetate, butylpropionate, amyl propionate, hexyl propionate, methyl-isopropyl ketone,methyl-isobutyl ketone, di-isobutyl ketone, and butyl oxide.
 5. Aprocess according to claIm 3, wherein the organic diluent is butylacetate.
 6. A process according to claim 1, which is arranged to becontinuously operated, the organic phase used for the selectiveextraction of the aqueous solution being regenerated by being placed incontact with a second aqueous phase selected from water and wateracidified by hydrochloric acid, and used for a new extraction.
 7. Aprocess according to claim 6, applied to the separation of cobaltchloride from nickel chloride aqueous solutions and operated in amulti-stage operation providing several distinct organic phases, saidsecond aqueous phase being used for the successive regeneration of saiddistinct organic phases until the concentration of cobalt chloride inthe said second aqueous phase reaches 130 grams per liter.
 8. A processaccording to claim 1, wherein the tri-alkylsulfonium chloride conformsto the formula wherein R1 is a CH3 radical and R2 and R3 are alkylradicals of from seven to 13 carbon atoms.